[release-branch.go1.5] cmd/compile: do not let regopt use REGTMP on ppc64
ppc64 codegen assumes that it is OK to stomp on r31 at any time, but it is not
excluded from the set of registers that regopt is allowed to use.
Fixes #12597
Change-Id: I29c7655e32abd22f3c21d88427b73e4fca055233
Reviewed-on: https://go-review.googlesource.com/15245
Reviewed-by: Minux Ma <minux@golang.org>
Reviewed-on: https://go-review.googlesource.com/16981
Run-TryBot: Austin Clements <austin@google.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>